Internal combustion (IC) engines may be incorporated into on-road vehicles for road applications or off-road vehicles for non-road applications. IC engines used in non-road applications are making increased use of electronics to meet emissions standards imposed by governmental regulations (e.g., Environmental Protection Agency (EPA)). The increased cost and complexity of advanced electrical systems to meet emissions requirements is offset by increased operational features available with the electronics. For example, increased use of electronics allows the use of alternative discrete torque curves and/or governor curves that are used under certain machine conditions. Non-road machines are capital goods and few, if any, customers would purchase a new machine if the only added “feature” of it's higher cost are lower emissions.
For a given IC engine, it is common to use a predefined torque curve with torque (load) as a function of engine speed. The torque curve used in operation defines the maximum output torque at a given engine speed. The torque or load is the rotational effort of the crankshaft of the engine, i.e., the output power. The engine speed is typically determined by the position of the throttle, either electronic or mechanical. For the corresponding engine torque, the engine controller controls operation of one or more engine control parameters to achieve the desired output torque. For example, the engine controller can control an exhaust gas recirculation (EGR) variable in an EGR system (such as a diluent-to-air ratio), a controllable element in a variable geometry turbocharger (VGT), a fuel injection timing, and/or a fuel pressure.
For a given IC engine, the engine is certified for emissions using the one or more discrete torque curves assigned to that engine. The emissions certification is expensive and must be done for each torque curve; thus, the number of torque curves assigned to an engine are kept to a bare minimum.
What is needed in the art is a method and system for potentially using a large number of torque curves for an IC engine, without having to recertify the emissions for the engine for each separate torque curve.